Tagged Questions
0
votes
2answers
59 views
Limit on velocity in Minkowski Spacetime geometry
Let A be a rocket moving with velocity v.
Then the slope of its worldline in a spacetime diagram is given by c/v.
Since it is a slope, c/v = tan(theta) for some theta > 45 and theta < 90.
Does ...
0
votes
2answers
77 views
If inherent randomness exist in quantum mechanics, what then of eternalism implied by relativity?
I am nothing but a curious layman so don't go too technical on me.
First of all, I am well aware that a lot of people consider the question of determinism vs indeterminism to be unsolved and others ...
4
votes
2answers
136 views
How do Doppler Effect and Time Dilation differ?
Above, I have drawn a diagram showing Doppler Effect (here we are using space-time but in a non-relativistic sense. Time and distance are the same for A and B).
Edit: I am adding a relativistic ...
-2
votes
1answer
63 views
How would time duration and space distance change when we move in the speed of light? [closed]
It is possible to figure out how time duration and space distance change when we are close to the speed of light - but I am not sure what happens to them if we travel in the speed of light.
2
votes
0answers
75 views
Car parking special-relavity puzzle
Hi I read the following puzzle from an old text book long time ago. However it doesn't provide the answer. So what is the solution?
Let's suppose a car is going to park to a garage and the garage is ...
3
votes
3answers
309 views
Why do clocks measure arc-length?
Apologies in advance for the long question.
My understanding is that in GR, massive observers move along timelike curves $x^\mu(\lambda)$, and if an observer moves from point $x^\mu(\lambda_a)$ to ...
1
vote
1answer
93 views
The status / acceptance of block time?
What is the current status or acceptance of block time as it relates to Einstein's theory of relativity? Has quantum mechanics ruled it out or is it still the favored view of the world? Perhaps there ...
0
votes
1answer
154 views
The real meaning of time dilation
Is this true or false: If A and B have clocks and are traveling at relative velocity to each other, then to B it APPEARS that A's clock moving slower, but A sees his own clock moving at normal speed.
...
4
votes
3answers
159 views
Setting up a local-coordinate system in space-time using only a single clock and light beams
I have a question to ask about the operationalist view of space-time. I am a mathematician who happens to be interested in physics, so if anyone thinks that my question is a silly or vague one, please ...
0
votes
0answers
83 views
Alternate derivation of kinetic mass increase in special relativity, from Maudlin
I've recently come across a derivation, which I've not seen before, of mass increase in special relativity. It seems to make sense, but I get tripped-up on an intermediate step, and I can't seem to ...
0
votes
2answers
59 views
Why does isotropy principle require existence of inertial transformation when axes are reversed?
Assuming one spatial and one termporal dimension, let's assume an intertial transformation $A(v)$ as follows:
$$
\begin{pmatrix}
t' \\
x' \\
\end{pmatrix} = A(v)
\begin{pmatrix}
t \\
x \\
...
5
votes
1answer
209 views
Is there any uncertainty between mass and proper length or time?
I was trying to naively draw a parallel between special relativity and the Heisenberg uncertainty principle. I try to understand uncertainty principle as a consequence of 4-position and 4-momentum ...
10
votes
4answers
345 views
The definition of an inertial reference frame in Einstein's relativity
I'm reading Sean Carroll's book on general relativity, and I have a question about the definition of an inertial reference frame. In the first chapter that's dedicated to special relativity, the ...
0
votes
1answer
196 views
Calculating the speed of an object moving relative to another moving Object (Frame of reference) [duplicate]
Possible Duplicate:
How to deduce the theorem of addition of velocities?
Let's say that you are in a rocket speeding at 90% the speed of light away from Earth. Now fire a bullet inside the ...
0
votes
0answers
77 views
Sequence of events in special relativity [closed]
I am taking a general education course on special relativity, and get quite confused by problems asking about which event happens first according to different observers. Is there an effective way to ...
5
votes
2answers
379 views
What's the difference between space and time?
I'm having a hard time understanding how changing space means changing time. In books I've read people are saying "space and time" or "space-time" but never explain what the difference is between the ...
1
vote
2answers
147 views
Special relativity, spacetime, velocity and units
We all know that space and time are the fundamental units, means no mathematical expression can express their relation to other variable fundamentally. But as we know that moving rod has a contracted ...
0
votes
1answer
114 views
Time Contraction
This is my first time posting on this site. I am a computer programmer that stumbled across a physics text book and have a question on special relativity. So firstly, I understand that there is no ...
3
votes
0answers
78 views
How would an observer perceive movement on a train that's travelling near the speed of light?
Person A is on Earth and a train (or whatever you want to imagine) travels past him at near the speed of light. How would person A perceive movement on the ship? If time is slowed on the ship from the ...
12
votes
9answers
444 views
How to explain (pedagogically) why there is 4 spacetime dimensions while we see only the 3 spatial dimesions?
I have been asked this question by a student, but I was able and in the same time incapable to give a good answer for this without equations, so do you have ideas how one can explain this in a simple ...
2
votes
2answers
174 views
What equations do I use to do basic time dilation problems?
I understand the concepts of relativity, but I don't know where to go to set up equations to do any actual calculations. For example, what equations would I use to find out the following:
A ship ...
3
votes
2answers
223 views
The order of seeing event in different spacetimes
Assume this question:
Three events A, B, C are seen by observer O to occur in the order ABC. Another observer O$^\prime$ sees the events to occur in the order CBA. Is it possible that a third ...
15
votes
3answers
740 views
What is the length of 1 second in meters
If time is treated as a fourth dimension of spacetime, what is relation between length and time units?
Or in other words, how can I convert time units to length units, for instance seconds to meters?
...
1
vote
1answer
71 views
Is it best to look at light as a particle when trying to understand special relativity?
So my course about special relativity explains time dilation using a moving train, where one sends up (i.e. perpendicular to the direction of movement) a light pulse which gets reflected etc. (a ...
2
votes
4answers
341 views
Why are objects at rest in motion through spacetime at the speed of light?
I read that an object at rest has such a stupendous amount of energy, $E=mc^2$ because it's effectively in motion through space-time at the speed of light and it's traveling through the time dimension ...
-6
votes
1answer
196 views
Speed of light is not fixed?
In my research, I found that the speed of light is not fixed. IS it true?
Namely, We know that light refracts when the medium it travels through changes. Actually, light travels in the same medium ...
3
votes
1answer
131 views
Hamiltonians and Lagrangians, Euclidean and Hyperbolic: Are they related?
The Lagrangian of a system is the difference between its kinetic energy $T$ and potential energy $V$, and is relativistically invariant:
$L = T - V$
The Hamiltonian of the same system is the sum ...
-1
votes
1answer
165 views
Time dilation at the speed of light
Does a massless particle travelling at the speed on light in a vacuum (c) experience an infinite time dilation effect?
i.e. Would the time dilation extend from the perspective of the massless ...
7
votes
4answers
508 views
Does the “Andromeda Paradox” (Rietdijk–Putnam-Penrose) imply a completely deterministic universe?
Wikipedia article: http://en.wikipedia.org/wiki/Rietdijk–Putnam_argument
Abstract of 1966 Rietdijk paper:
A proof is given that there does not exist an event, that is not already in the past for ...
1
vote
2answers
248 views
What does a closed time-like curve look like?
I want to see a plot of closed time-like curve in $(t,x)$.
$t$ - vertical axis
$x$ horizontal axis
(the usual setting just neglect $y$ and $z$ components of $(t,x,y,z)$).
What does it look like?
2
votes
4answers
314 views
Reducing General Relativity to Special Relativity in limiting case
I understand that general relativity is applicable to gravitational fields and special relativity is applicable to case when there is no gravity. But is there a derivation on how to reduce General ...
4
votes
2answers
374 views
Can an “absolute” frame of reference be determined by measuring the compression of light?
General relativity tells us that there is no absolute frame of reference (actually, it tells us that all frames are relative, which is close but not the same as there is no absolute frame).
Special ...
3
votes
2answers
360 views
Why is time special?
In Special Relativity, the spacetime interval between two events is $s^2 = -(c{\Delta}t)^2+({\Delta}x)^2+({\Delta}y)^2+({\Delta}z)^2$ giving the Minkowski metric $\eta_{\mu\nu}=\text{diag}(-1, 1, 1, ...
1
vote
0answers
111 views
Einstein's postulates <==> Minkowski space. In layman's terms [duplicate]
Possible Duplicate:
Einstein's postulates <==> Minkowski space. (In layman's terms)
In the spirit of Einstein's arguments using flashes of light, moving trains and mirrors;
...
15
votes
4answers
1k views
Einstein's postulates <==> Minkowski space. (In layman's terms)
What's the cleanest/quickest way to go between Einstein's postulates [1] of
Relativity: Physical laws are the same in all inertial reference frames.
Constant speed of light: "... light is always ...
3
votes
3answers
400 views
Rotations in space-time
In Landau's Classical Theory of Fields, one finds the statement:
Every rotation in the four-dimensional space can be resolved into six
rotations, in the planes $xy,zy,xz,tx,ty,tz$ (just as every ...
9
votes
2answers
767 views
Invariant spacetime - distance - Circular Motion
I understand that the closer something travels to the speed of light, that time will stretch by a factor, and distance will compress by the same factor.
My question is, if something travels in a ...
4
votes
2answers
532 views
How do I develop an intuitive model of spacetime?
I am your nightmare poster - a layman trying to learn special relativity. (I'm also a refugee from stackoverflow.com: trust me, it's only going to get worse). Apologies in advance if my question is ...
3
votes
3answers
2k views
Example of space-like intervals in spacetime
From wikipedia:
When a space-like interval separates
two events, not enough time passes
between their occurrences for there to
exist a causal relationship crossing
the spatial distance ...
